Method of rebuilding a cathode-ray tube

ABSTRACT

A bulb member and a neck are assembled using a confined light beam within the cathode-ray tube to visually define a central longitudinal axis of the tube. The visually-defined central longitudinal axis passes through a point at the geometric center of the viewing-screen structure and through at least one point on the central longitudinal axis of the neck.

United States Patent [191 Fassett 1 51 June 18, 1974 METHOD OF REBUILDING A CATHODE-RAY TUBE [75] Inventor: Gardner Luther Fassett, Lancaster,

[73] Assignee: RCA Corporation, New York, NY.

[22] Filed: May 31, 1973 [21] App]. N0.: 365,755

[52] US. Cl 29/2513, 316/2, 316/29 [51] Int. Cl. H0lj 9/18 [58] Field of Search 316/1, 2, 29, 28, 31;

[5 6] References Cited UNITED STATES PATENTS 2,923,097 2/1960 Hellinger 65/28 X 3,594,059 7/1971 Holz 316/28 Primary Examiner-Roy Lake Assistant Examiner-James W. Davie Attorney, Agent, or FirmG. H. Bruestle; L. Greenspan [57] ABSTRACT A bulb member and a neck are assembled using a confined light beam within the cathode-ray tube to visually define a central longitudinal axis of the tube. The visually-defined central longitudinal axis passes through a point at the geometric center of the viewing-screen structure and through at least one point on the central longitudinal axis of the neck.

7 Claims, 4 Drawing Figures PHENTEB Jul B SHEEI 2 BF 4 METHOD OF REBUILDING A CATHODE-RAY TUBE BACKGROUND OF THE INVENTION This invention relates to a method of rebuilding a cathode-ray tube and particularly, but not exclusively,

to a method of rebuilding a television picture tube having the original neck and mount removed.

A television picture tube may be rebuilt by opening the tube to atmospheric pressure and then cracking off the original neck with the mount therein on a circumferential scribe line at the neck, as is known. A replacement neck is then assembled to the remaining tube portion or bulb member. Then a new mount is assembled therein, and the tube is further processed.

In prior methods of rebuilding a tube, the geometric center of the small end of the bulb and the geometric center of the yoke-receiving portion of the bulb, or the geometric center of the large end of the bulb, are mechanically located on a line which defines the axis of the bulb member. Then the neck axis is mechanically located, and it is made coincident with the bulb axis. The bulb member and the neck are then permanently attached. Although ideally these methods provide a properly-aligned bulb member and a neck, this does not consistently occur in practice. This is because the yoke-receiving portion of the bulb or the small end of the bulb member which are used to mechanically locate the tube may not be concentric with the tube axis; or the distance between the small end of the bulb member and the yoke-receiving portion of the bulb may be too short to generate a satisfactory axis; any of which may prevent alignment of the bulb member and neck on a coincident axis. This may result in the neck axis being tilted from the desired direction in which it is directed through the center of the viewing-screen structure. A tube having a tilted neck axis will increase the possibility that the mount will be incorrectly aligned with the screen which may result in an unsatisfactory operation of the tube in a receiver. Furthermore, after the bulb member and neck are attached by the prior methods, it is very difficult to determine if the neck axis is properly aligned to pass through the center of the viewing-screen structure.

SUMMARY OF THE INVENTION The novel method is used to assemble a bulb member and a neck for a cathode-ray tube. A bulb member and a neck are loosely positioned with the geometric longitudinal axes thereof on a line. The point at the geometric center of the viewing-screen structure and at least one point on the geometric longitudinal axis of the neck are defined. Then, a confined light beam is projected within the tube, and the bulb member and neck are moved until the confined light beam is directed through each of the defined points to visually define the central longitudinal axis of the tube. Then the bulb member and neck are permanently attached. The use of a confined light beam directed through the point at the geometric center of the viewing-screen structure and at least one point on the geometric central axis of the neck permits a visual determination of proper alignment, both prior and subsequent to attachment of the replacement neck. This consistently provides an accu rately assembled tube. The method also permits subsequent checking of the alignment after sealing which permits scrapping improperly aligned assemblies and results in economies in rebuilding cathode-ray tubes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a television picture tube assembled by the novel method.

FIG. 2 is the tube of FIG. 1 illustrating one embodiment of the novel method of assembling a cathode-ray tube using a confined-light beam to visually define a central longitudinal axis of the tube.

FIG. 3 illustrates the embodiment shown in FIG. 2 wherein the central longitudinal axis of the mount is aligned with the visually-defined central longitudinal axis of the tube.

FIG. 4 illustrates another embodiment of the novel method similar to that shown in FIG. 2 for visually defining a central longitudinal axis of the tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a color television picture tube 10 having a central longitudinal axis A--A. The tube 10 comprises a faceplate 11, a funnel 12 and a neck 13. A viewing-screen structure, hereafter called screen 14, is deposited on the inner surface of the faceplate 11. A mount assembly, hereafter called mount 15, also has a central longitudinal axis B--B. The mount 15 comprises a multiple electron-gun assembly, hereafter called electron gun 16, a stem 17 and an exhaust tubulation 18. The electron gun 16 includes at least three centering members or centering means 19 at the forward end 20 to center the forward end of the electron gun 16 within the neck 13. The electron gun 16 is adapted to project electron beams towards the screen 14. The electron beams aredirected within the neck 13 to strike substantially the center of the screen 14. The mount 15 is assembled in the neck 13 with the central longitudinal axis 8-8 of the mount 15 coincident with the central longitudinal axis A--A of the tube 10.

When the tube 10, shown in FIG. 1, becomes inoperative, it may be rebuilt by removing and discarding a portion of the neck 13 with the mount 15 therein and providing a new neck and mount. In rebuilding a tube 10, it is critical that a bulb member 22 and a neck 13 are assembled with the central longitudinal axes thereof coincident and passing through a point at the center of the screen 14.

The novel method describes rebuilding a tube on either a combination neck-sealing mount-sealing machine as described inExample 1. or on a separate necksealing machine and a separate mount sealing machine as described in Example 2. When the bulb-neck assembly, assembled by the method of Example 1, is moved to a separate mount-sealing machine, the visuallydefined central longitudinal axis may not be reestablished for the reasons which will be described. The method of Example 2 permits accurate reestablishment of the central longitudinal axis on a separate mountsealing machine. The only difference between the methods of Example 1 and Example 2 is that the method of Example 1 does not provide for the reestablishment of the visually-defined central longitudinal axis on some separate machines.

EXAMPLE 1 The first embodiment of the novel method is used on a combination mount-sealing neck-sealing machine as previously described. A bulb member 22 and a neck 13 are loosely positioned in an approximate aligned relationship where the geometric longitudinal axis C-C of the bulb member 22 and the geometric longitudinal axis DD of the neck 13 substantially coincide on a line as shown in FIG. 2.

The point 25 at the geometric center of the screen 14 is now defined. The preferred method of defining the point 25 is to form a first opaque masking member 33 having a central aperture 34 therethrough of a plastic or similar material to conform to and fit over the faceplate II. The first masking member 33 is positioned over the faceplate 11 as shown in FIG. 2, so that the central aperture 34 defines the point 25 at the geometric center of the faceplate 11 and screen 14. The preferred size of the central aperture 34 is about 0.60 inch in diameter.

The second point 26 at the geometric longitudinal axis of the neck 13 at a second plane 24 is also defined. The second plane 24 is substantially perpendicular to the geometric longitudinal axis DD. A second selfcentering opaque masking member 35 having a central aperture 36 therethrough is positioned within the neck 13 at the plane 24. The central aperture 36 defines the point 26 at the geometric center of the neck 13. The preferred size of the central aperture 36 is about 0.030 inch in diameter. The preferred longitudinal location of the second plane 24 is at the future position of the forward centering means 19.

Additional points along the central longitudinal axis of the tube may also be defined. The third point 30 is defined at the geometric center of the bulb member 22 at a third plane 27, the fourth point 31 is defined at the geometric center of the neck 13 at a fourth plane 28, and the fifth point 32 is defined at the geometric center of the neck 13 at the fifth plane 29. The points 26, 31 and 32 are substantially on the central longitudinal axis DD of the neck 13.

After the geometric center at each of the points 25 and 26 is defined, a confined light beam is projected within the tube 10. In the preferred embodiment, the confined light beam is produced by a light source 37 positioned within the tube 10 as shown in FIG. 2. It is preferred that the light source 37 is a laser light source. The preferred size of the confined light beam provided by the laser light source is about 0.030 inch in diameter.

The bulb member 22 and the neck 13 are then moved until the confined light beam 38 is directed to pass through each of the apertures 34 and 36. When the confined light beam 38 passes through the apertures 34 and 36, it very simply defines the central longitudinal axis AA of the tube 10. During movement of the bulb member 22 and neck 13, it is very easy to observe when the light beam strikes the screen 14, since the screen 14 is generally comprised of a plurality of phosphor dots and a group of these dots is illuminated by the confined light beam. In practice, where the dots are about 0.006 inch in diameter and spaced about 0.018 inch, a hexagonal group of seven dots is illuminated by the confined light beam. In the novel method, the bulb member 22 and neck 13 are moved until this group of lightemitting dots is visually observed to be illuminated by the confined light beam. confined light beam.

It is preferred that the points 30 and 31 respectively also coincide on the visually-defined'axis AA, but this is not critical. It is only necessary that the bulb member 22 and neck 13 are assembled substantially on a straight line and not bent more than one-half degree from a straight line at the location of the connecting ends of the bulb member 22 and neck 13.

After the confined light beam passes through each of the points 25 and 26, the bulb member 22 and the neck 13 are permanently attached as by sealing.

After the neck 13 is sealed to the bulb member 22, the coincidence of the axis C--C and DD can easily be rechecked by observing if the confined light beam continues to illuminate the phosphor dots at the geometric center of the screen 14 as viewed through the aperture 34 in the masking member 33. If it does, then the bulb member 22 and neck 13 are properly aligned with a visually-defined central longitudinal axis AA passing through the point 25 at the geometric center of the screen 14.

The sealed tube 10 is then supported by external clamping means (not shown) on the same sealing machine, taking care not to move the tube 10. This maintains the visually-defined central longitudinal axis AA aligned on the combination machine. After the tube is supported by external clamping means the alignment can be again visually rechecked as described above. The second masking member 35 and the light source 37 are then removed from the tube 10.

A mount 15 is then inserted within the tube 10 to a desired longitudinal location such that the central longitudinal axis B-B of the mount 15 is substantially coincident with the axis AA of the tube 10. At the coincident position, the point 32 at the geometric center of the stem 17 is on the axis AA. The forward end 20 of the electron gun 16 is also centered within the neck 13 by the electron-gun-centering means 19 because the neck 13 and bulb member 22 are assembled with the point 26 on the central longitudinal axis AA of the tube 10. The mount 15 is then permanently attached to the neck 13 as by sealing at the stem 17, as shown in FIG. 3.

EXAMPLE 2 In a second embodiment of the novel method the only difference from the method of Example 1 is that a sixth point 40 (see FIG. 4) at the geometric center of either the bulb member 22 or the neck 13 at a sixth longitudinal location must be selected. This is required where a separate mount-sealing machine is used for sealing the mount within the tube.

Clearly, one method to reestablish the axis AA on the mount-sealing machine is to use the points 25 and 26 to reestablish the axis AA. But, this requires clamping the neck 13 in a neck chuck at the plane 24 which passes through the point 26. This is not practical on some mount-sealing machines since this location is too near the sealing fires. The use of a neck chuck 21 at this location may result in the neck 13 cracking or in an improper annealing of the neck 13. If the neck 13 is clamped at other longitudinal locations, the visuallydefined axis AA may not be reestablished since the plane 24 is the only longitudinal location where the point 26 at the geometric center of the neck 13 exactly coincides with the visually-defined axis AA.

The use of three points is therefore necessary to permit reestablishing the visually-defined axis AA within practical design limitations of some mount-sealing machines. After the axis AA is reestablished, the mount 15 is assembled coincident therewith.

The bulb member 22 and neck 13 are loosely positioned on a neck-sealing machine, and the first and second points 25 and 26 are defined as described in Example l.

The sixth point 40 on the geometric longitudinal axis of the neck 13 is defined at a sixth plane 39. The sixth plane 39 is also substantially perpendicular to the geometric longitudinal axis AA. A third self-centering masking member 41 is positioned at the plane 39 of the future position of the neck chuck 21 as shown in FIG. 4. The third masking member 41 also includes an aperture 42 therethrough to correspond with the sixth point 40 at the geometric center of the neck 13. The preferred size of the aperture 42 is about 0.030 inch in diameter. The preferred longitudinal location for the point 40 is at the future position of the neck chuck 21 used on the mount-sealing machine (not shown).

After the geometric center of each of the points 25, 26 and 40 is defined, a confined light beam is projected within the tube, as described in Example 1.

The bulb member 22 and the neck 13 are then moved until the confined light beam 38 is directed to pass through each of the apertures 34, 42 and 36. This very simply defines the central longitudinal axis AA of the tube as shown in FIG. 4.

The second and third masking members 35 and 41 respectively and the light source 37 are then removed from the tube. The sealed bulb member and neck are then removed from the neck-sealing machine and positioned on the mount-sealing machine. The mountsealing machine reestablishes the visually-defined central longitudinal axis AA by supporting the assembly at the screen 14 and at the position of the neck chuck 21.

The mount 15 is now inserted in the tube 10 with the central longitudinal axis of the mount coincident with the reestablished central longitudinal axis of the tube 10 in a manner similar to that shown in FIG. 3 for example I. At the coincident position of the tube and the mount 15, the point 32 at the geometric center of the stem 17 is on the axis AA for the same reason described in Example 1. The stem 17 is then attached as by sealing to the neck 13.

GENERAL CONSIDERATIONS AND ALTERNATIVES In the novel method, the bulb length will always remain the same, but different-length necks may be used. Since a longer neck or a shorter neck may be used, the point 40 previously described may be either in the bulb member or in the neck. It is not important whether the plane 39 is at a locationalong thebulbmember 22 or along the neck 13 in the novel method. But it is preferred that the actual seal does not occur at the plane 39 since this may interfere with the reestablishment of the tube axis AA on the mount-sealing machine.

Although the masking members are described as opaque, they may be transparent and have markings thereon which may describe the desired geometric center area through which the confined light beam is directed to visually define the central longitudinal axis of the tube.

I claim:

1. A method of rebuilding a cathode-ray tube including a viewing-screen structure, a bulb member and a neck, said method comprising the steps of a. loosely positioning a bulb member and a neck with the geometric longitudinal axes thereof approximately in line,

b. defining a point at the geometric center of the viewing-screen structure,

c. defining at least one point on the geometric longitudinal axis of the neck,

d. projecting a confined light beam within said tube,

e. then moving said bulb member and said neck until said confined light beam is directed to pass through each of said defined points to visually define the central longitudinal axis of said tube,

f. and then permanently attaching said bulb member and said neck.

2. The method defined in claim 1 wherein said tube includes a mount including the additional steps of g. then, inserting the mount within said neck to a desired longitudinal location with the central longitudinal axis thereof substantially coincident with the visually-defined central longitudinal axis of said tube,

h. and then permanently attaching said mount and said neck.

3. The method defined in claim ll wherein said mount includes an electron gun having forward centering means, said step (c) comprising defining the point at the geometric center of said neck at a first reference plane at the future longitudinal location of said forward centering means.

4. The method defined in claim 3 wherein said tube is supported during mount sealing by external centering means, said step (c) comprising defining an additional point at the geometric center of said neck at a second reference plane at the future longitudinal location of said external centering means.

5. A method of assembling a cathode-ray tube including a viewing-screen structure, a bulb member, a neck, and a mount having forward centering means, said method comprising the steps of a. loosely positioning a bulb member and a neck with the geometric longitudinal axes thereof approximately on a line,

b. selecting a first reference plane through the geometric center of the viewing-screen structure, said first reference plane substantially perpendicular to the geometric central longitudinal axis of the bulb,

c. selecting a second reference plane through the neck at the future location of the forward centering means, said second reference plane substantially perpendicular to the geometric central longitudinal axis of the bulb,

d. positioning at each of said selected reference planes an opaque masking member having a central aperture therethrough, said apertures defining the point at the geometric center of said bulb member or said neck,

e. projecting a confined light beam within said tube,

f. then moving said bulb member and said neck until said confined light beam is directed through each of said central apertures of said masking members to visually define the central longitudinal axis of said tube,

7 g. then, while maintaining said adjusted position, permanently attaching said bulb member to said neck.

6. The method defined in claim wherein said tube is assembled on a machine having external support means, said method including the additional steps of h. supporting said bulb with external support means,

i. removing said masking members,

j. then, inserting a mount within said neck to a desired longitudinal location with the central longitudinal axis of said mount substantially coincident tudinal axis of the bulb or the neck. 

1. A method of rebuilding a cathode-ray tube including a viewing-screen structure, a bulb member and a neck, said method comprising the steps of a. loosely positioning a bulb member and a neck with the geometric longitudinal axes thereof approximately in line, b. defining a point at the geometric center of the viewingscreen structure, c. defining at least one point on the geometric longitudinal axis of the neck, d. projecting a confined light beam within said tube, e. then moving said bulb member and said neck until said confined light beam is directed to pass through each of said defined points to visually define the central longitudinal axis of said tube, f. and then permanently attaching said bulb member and said neck.
 2. The method defined in claim 1 wherein said tube includes a mount including the additional steps of g. then, inserting the mount within said neck to a desired longitudinal location with the central longitudinal axis thereof substantially coincident with the visually-defined central longitudinal axis of said tube, h. and then permanently attaching said mount and said neck.
 3. The method defined in claim 1 wherein said mount includes an electron gun having forward centering means, said step (c) comprising defining the point at the geometric center of said neck at a first reference plane at the future longitudinal location of said forward centering means.
 4. The method defined in claim 3 wherein said tube is supported during mount sealing by external centering means, said step (c) comprising defining an additional point at the geometric center of said neck at a second reference plane at the future longitudinal location of said external centering means.
 5. A method of assembling a cathode-ray tube including a viewing-screen structure, a bulb member, a neck, and a mount having forward centering means, said method comprising the steps of a. loosely positioning a bulb member and a neck with the geometric longitudinal axes thereof approximately on a line, b. selecting a first reference plane through the geometric center of the viewing-screen structure, said first reference plane substantially perpendicular to the geometric central longitudinal axis of the bulb, c. selecting a second reference plane through the neck at the future location of the forward centering means, said second reference plane substantially perpendicular to the geometric central longitudinal axis of the bulb, d. positioning at each of said selected reference planes an opaque masking member having a central aperture therethrough, said apertures defining the pOint at the geometric center of said bulb member or said neck, e. projecting a confined light beam within said tube, f. then moving said bulb member and said neck until said confined light beam is directed through each of said central apertures of said masking members to visually define the central longitudinal axis of said tube, g. then, while maintaining said adjusted position, permanently attaching said bulb member to said neck.
 6. The method defined in claim 5 wherein said tube is assembled on a machine having external support means, said method including the additional steps of h. supporting said bulb with external support means, i. removing said masking members, j. then, inserting a mount within said neck to a desired longitudinal location with the central longitudinal axis of said mount substantially coincident with said visually-defined central longitudinal axis of said tube, k. and then, permanently attaching said mount and said neck.
 7. The method defined in claim 5 including the additional step between steps (c) and (d) of l. selecting a third reference plane through the neck at one other location along said bulb member or said neck, said third reference plane being substantially perpendicular to the geometric central longitudinal axis of the bulb or the neck. 